Set enable-timestamps by default is max-rtt-penalty is positive.

babeld.man

@@ -333,7 +333,12 @@ packet loss is expected.  The default is four times the hello interval.
 .BR enable\-timestamps " {" true | false }
 Enable sending timestamps with each Hello and IHU message in order to
 compute RTT values.  The default is
-.BR false .
+.B true
+if
+.B max\-rtt\-penalty
+is non-zero (see below), and
+.B false
+otherwise.
 .TP
 .BI rtt\-exponential\-decay " decay"
 This specifies the decay factor for the exponential moving average of

interface.c

@@ -293,9 +293,6 @@ interface_up(struct interface *ifp, int up)
         if(IF_CONF(ifp, faraway) == CONFIG_YES)
             ifp->flags |= IF_FARAWAY;
 
-        if(IF_CONF(ifp, enable_timestamps) == CONFIG_YES)
-            ifp->flags |= IF_TIMESTAMPS;
-
         if(IF_CONF(ifp, hello_interval) > 0)
             ifp->hello_interval = IF_CONF(ifp, hello_interval);
         else if((ifp->flags & IF_WIRED))
@@ -327,6 +324,11 @@ interface_up(struct interface *ifp, int up)
         }
         ifp->max_rtt_penalty = IF_CONF(ifp, max_rtt_penalty);
 
+        if(IF_CONF(ifp, enable_timestamps) == CONFIG_YES ||
+           (IF_CONF(ifp, enable_timestamps) == CONFIG_DEFAULT &&
+            ifp->max_rtt_penalty > 0))
+            ifp->flags |= IF_TIMESTAMPS;
+
         if(ifp->ll)
             free(ifp->ll);
         ifp->numll = 0;